Expose additional storage options

Store following storage-related options in expvar:
- memory.max-traces
- downsampling.ratio

Signed-off-by: Daniil Rutskiy <dstdfx@gmail.com>

plugin/storage/factory.go

@@ -16,6 +16,7 @@
 package storage
 
 import (
+	"expvar"
 	"flag"
 	"fmt"
 	"io"
@@ -81,6 +82,7 @@ func NewFactory(config FactoryConfig) (*Factory, error) {
 		}
 		f.factories[t] = ff
 	}
+	f.setExpvarOptions()
 	return f, nil
 }
 
@@ -249,3 +251,9 @@ func (f *Factory) Close() error {
 	}
 	return multierror.Wrap(errs)
 }
+
+func (f *Factory) setExpvarOptions() {
+	if expvar.Get(downsamplingRatio) == nil {
+		expvar.NewInt(downsamplingRatio).Set(int64(f.FactoryConfig.DownsamplingRatio))
+	}
+}

plugin/storage/factory_test.go

@@ -17,6 +17,7 @@ package storage
 
 import (
 	"errors"
+	"expvar"
 	"flag"
 	"fmt"
 	"io"
@@ -350,6 +351,18 @@ func TestParsingDownsamplingRatio(t *testing.T) {
 	assert.Equal(t, f.FactoryConfig.DownsamplingRatio, 0.5)
 }
 
+func TestSetExpvarOptions(t *testing.T) {
+	clearEnv()
+	defer clearEnv()
+
+	f, err := NewFactory(defaultCfg())
+	require.NoError(t, err)
+
+	gotDownsamplingRatio := expvar.Get(downsamplingRatio)
+
+	assert.Equal(t, f.DownsamplingRatio, gotDownsamplingRatio)
+}
+
 type errorCloseFactory struct {
 	closeErr error
 }

plugin/storage/memory/options.go

@@ -15,6 +15,7 @@
 package memory
 
 import (
+	"expvar"
 	"flag"
 
 	"github.com/spf13/viper"
@@ -37,4 +38,11 @@ func AddFlags(flagSet *flag.FlagSet) {
 // InitFromViper initializes the options struct with values from Viper
 func (opt *Options) InitFromViper(v *viper.Viper) {
 	opt.Configuration.MaxTraces = v.GetInt(limit)
+	opt.setExpvarOptions()
+}
+
+func (opt *Options) setExpvarOptions() {
+	if expvar.Get(limit) == nil {
+		expvar.NewInt(limit).Set(int64(opt.Configuration.MaxTraces))
+	}
 }

plugin/storage/memory/options_test.go

@@ -15,6 +15,8 @@
 package memory
 
 import (
+	"expvar"
+	"strconv"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -30,3 +32,15 @@ func TestOptionsWithFlags(t *testing.T) {
 
 	assert.Equal(t, 100, opts.Configuration.MaxTraces)
 }
+
+func TestOptionsWithFlags_CheckExpvarOptions(t *testing.T) {
+	v, command := config.Viperize(AddFlags)
+	command.ParseFlags([]string{"--memory.max-traces=100"})
+	opts := Options{}
+	opts.InitFromViper(v)
+
+	gotMaxTraces, err := strconv.Atoi(expvar.Get("memory.max-traces").String())
+	assert.NoError(t, err)
+
+	assert.Equal(t, 100, gotMaxTraces)
+}